The chemical synthesis of 2 feet (3 feet)-O-aminoacyl and 2 feet (3 feet)-O-(N-acylaminoacyl) oligoribonucleotides with nucleotide sequences identical to or resembling those of the 3 feet-terminus of AA-tRNA will be carried out. The aminoacyl ologonucleotide models will be used for investigations of substrate specificity of peptidyltransferase sites of procaryotic and eucaryotic ribosomes including those obtained from the neoplastic cells. The ribosomes from E. coli will be specifically modified at the peptidyltransferase catalytic center and the competency of these modified particles in, e.g., peptidyltransferase reaction, substrate binding, EF-Tu dependent GTPase will be investigated. The aminoacyl oligonucleotides will be also used as models for investigations of the interactions of the 3 feet-terminus of AA-tRNA with E. coli elongation factor Tu and for the study of the role of elongation factor P. Collectively, these studies should contribute to the understanding of the molecular mechanism of AA-tRNA interaction with the ribosome or elongation factors, the mechanism of synthesis of peptide bonds on the ribosome and the mechanism of EF-Tu dependent GTPase.